The heat exchangers for cooling medium condensing apparatuses conventionally include three types, namely, the air cooling type, the water cooling type and the evaporative type. It is known that heat dissipation efficiency of a water cooling type heat exchanger is slightly better than air cooling type ones, but the heat dissipation efficiency of an evaporative cooling type heat exchanger is much better than a water cooling type because one liter of water absorbs 1 Kcal of heat when raising 1xc2x0 C., but absorbs 539 Kcal when evaporated.
In addition the cooling efficiency by directly dissipating heat from coil tubes should be better than by indirectly dissipating heat from cooling fins which the heat has to be transferred to cooling fins from coil tubes first.
Therefor, the issue of how to insure a high evaporation efficiency for evaporating the water directly on the surface of tubes of the medium coil is an important problem to be solved.
Further more, a conventional heat exchanger composed of a plurality of cooling fins with a high density of 13 pieces per inch up to 17 pieces per inch, between which it will be easy to deposit dirt and sediment that will corrupt the cooling fins. The fins do not have enough spacing for cleaning and are inconvenient for maintenance.
The present invention solves the problem by utilizing a streamline cross sectional tube instead of a conventional round tube for a medium coil without cooling fins.
FIG. 1A shows a wind flow xe2x80x9cwxe2x80x9d blowing around a conventional round tube R having a water film thereon, which the wind xe2x80x9cwxe2x80x9d divides into two flows around the surface of both sides of the round tube respectively to a point F and Fxe2x80x2 at the rear portion after passed over the diameter DDxe2x80x2 thereof, then the wind flow leave the tube surface and pass directly to the back side, therefor the wind flow xe2x80x9cwxe2x80x9d does not blow over the surface of the arc FFxe2x80x2 to produce evaporating effects, it is a great loss of evaporative efficiency therefore, because the surface around the arc FFxe2x80x2 is almost larger than ⅓ of the surface of a whole tube, further more there will be a turbulence of eddy current xe2x80x9cCxe2x80x9d and a windless zone xe2x80x9cTxe2x80x9d that occurs at a rear space behind the tube that provides a poor cooling efficiency of the next row of tubes of the coil.
FIG. 1B shows a wind flow xe2x80x9cwxe2x80x9d blowing around a streamline tube S according to the present invention, wherein the wind flow blows toward a larger head portion of a streamline tube, the wind flow xe2x80x9cwxe2x80x9d is divided into two opposite paths around the streamline surface of the tube, and toward a gradually reduced rear portion where the wind flow blows around the streamline surface after passing over the diameter DDxe2x80x2 to an end edge xe2x80x9cExe2x80x9d. In the present invention, there will be no eddy current and windless zones. Furthermore, according to the theory of aerodynamics the wind speed will increase while the wind blows over the rear portion surface of the streamline tube from point D(andDxe2x80x2) to the end edge portion E and a negative pressure xe2x80x9cPxe2x80x9d will be provide at the edge point E so as to increase an amount of evaporative efficiency while a water film is held instantly on the surface of the tubes.
A Taiwanese utility model application S/N 7320299 shows that a streamline tube can be used for a heat exchanger. However the document does not define what type of heat exchanger has been utilized provides no further description of a practical technology to teach how to use it.
Meanwhile the present invention is quit different having defined a practical technology of heat exchanger without cooling fins by using streamline tubes for medium coils.
A coordinate non-pressure water feeding system is employed in the present invention to supply evaporative water for providing a water film held on the surface of the tubes for enough time to be fully evaporated therefrom.
Furthermore, in case of the evaporative efficiency is fully developed by the coil of streamline tubes itself, the numbers of indirect heat dissipation cooling fins can be greatly reduced to a minimum or fully omitted, therefore it will be easy to clean and convenient to maintain.
Therefore a major object of the present invention is to provide an evaporative heat exchanger for a condenser of an air conditioning system wherein the medium coil is composed of a plurality of streamline cross sectional tubes to instead conventional round tubes so as to increase the evaporative cooling efficiency.
Another major object of the present invention is to provide an evaporative heat exchanger wherein the numbers of conventional cooling fins can be greatly reduced or eliminated to avoid the use of cooling fins so as to reduce manufacturing costs.
Still another main object is to provide an evaporative heat exchanger without cooling fins which will be easy to clean and convenient to maintain.
The present invention relates to a coil assembly for use in a water evaporative type heat exchanger of a medium condensing cooling apparatus especially relates to a coil assembly having a plurality of streamline cross sectional tubes used instead of the conventional round cross sectional tubes to highly improve the evaporating efficiency and maintain a high E.E.R. thereof, in which the number of cooling fins can be greatly reduced or completely omitted to provide a bare coil that is easy to clean and convenient to maintain.